Polishing pad, polishing apparatus and method for polishing wafer

ABSTRACT

A polishing apparatus includes a belt-type surface plate stretched between two rollers each having a rotation shaft arranged in parallel to that of the other roller, a plurality of sheet-type polishing pads stuck on the surface plate, and a dresser for activating the polishing pads. Part of an upper end portion of each of the polishing pads facing an adjacent one of the polishing pads has an obtuse angle. Thus, the dresser is not caught by the upper end portion of each of the polishing pads, so that the generation of a scratch in the polishing pads. Therefore, a semiconductor wafer can be polished without causing a scratch thereon.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims priority under 35 U.S.C. § 119(a) on Japanese Patent Application No. 2003-182168, the entire contents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

[0002] The present invention relates to a method for polishing a wafer, a polishing pad, and a polishing apparatus using the polishing pad, and more particularly relates to an apparatus for performing chemical mechanical polishing (CMP) to a semiconductor wafer, a polishing pad for the apparatus, and a method for polishing a semiconductor wafer.

[0003] In recent years, the size of semiconductor devices has been markedly reduced. Various kinds of techniques used in methods for fabricating a semiconductor device, then, have been developed in order to reduce the size of semiconductor devices. Among such newly developed techniques, multi-layer interconnect technologies for stacking interconnect layers made of a metal interconnect material and an insulating material several times largely contribute to size reduction and function improvement of semiconductor devices. However, at the same time, newly developed techniques have many technical problems, as well. One of the problems is about how to ensure evenness of in each interconnect layer. For example, if evenness in each interconnect layer is not ensured to leave an uneven upper surface of each interconnect layer, a focus shift occurs in a photolithography process step which is a key to reduction in the size of a semiconductor device, so that an interconnect pattern can not be formed. To solve this problem, in recent years, chemical mechanical polishing (CMP) in which a surface of a semiconductor wafer is chemically and mechanically polished to form a fine surface has been used in many cases.

[0004] Two types of CMP apparatuses are generally known. One is a turntable polishing type CMP apparatus and the other is a belt polishing type CMP apparatus.

[0005]FIG. 15 is a schematic view illustrating the structure of a polishing mechanism portion of a known belt polishing type CMP apparatus.

[0006] In the CMP apparatus of FIG. 15, a plurality of sheet-type polishing pads 101 of which a base material is blowing polyurethane are stuck on a belt-type surface plate 102 so as to be spaced apart from one another. The surface plate 102 is scanned while a slurry, i.e., an abrasive is supplied to the polishing pads 101 and then a surface of a semiconductor wafer 104 which is attached to a carrier 103 pressed against the carrier 103 while the carrier 103 are rotated. Thus, the semiconductor wafer 104 is polished. Moreover, to activate (raise a nap on) upper surfaces of the polishing pads 101, a dresser 106 provided in a lower surface of a cylinder 105 is pressed against the polishing pads 101 so as to be shifted in the perpendicular direction with respect to the direction in which the surface plate 102 is scanned as necessary. By activating the upper surfaces of the polishing pads 101, the polishing pads 101 can maintain polishing ability.

[0007] Moreover, the known CMP apparatus includes a final detector (not shown) arranged so as to be surrounded by, for example, the belt-type surface plate 102. A through hole 110 for final detection is formed in each of the polishing pads 101. The final detector irradiates, for example, a laser beam to the semiconductor wafer 104 through the through hole 110 and receives reflected light to detect an end point of polishing.

[0008]FIG. 16 is an enlarged view of a portion E in the known CMP apparatus of FIG. 15 illustrating the through hole 110 for detecting a polishing end point. In this case, assume that the direction in which the surface plate 102 is scanned is referred to as the “length direction of the polishing pads 101” and a perpendicular direction to the surface plate 102 in the surface of each of the polishing pads 101 is referred to as the “width direction of the polishing pad 101”. Then, the through hole 110 is formed as an opening located around the center of each of the polishing pads 101 in the width direction.

[0009] Note that as shown in FIG. 15, there are a certain space between any two of the polishing pads 101 which are adjacent to each other in the forward direction. Thus, polishing wastes and the slurry can be quickly exhausted.

[0010] By using the above-described CMP apparatus, an upper surface of a semiconductor device can be made even with high accuracy. Therefore, a minute interconnect pattern can be formed.

SUMMARY OF THE INVENTION

[0011] When the known CMP apparatus is continuously used, as shown in FIG. 16, a scratch 107 is generated in part of an end portion of each of the polishing pads 101 facing an adjacent one of the polishing pads 101. In the same manner, a scratch 107 is also generated in a periphery portion of the through hole 110 of FIG. 16 in polishing. The scratch 107 is generated due to collision of the dresser 106 with the polishing pads 101 when dresser 106 is moved as necessary in a perpendicular direction with respect to a scanning direction of the surface plate 102.

[0012] Moreover, as shown in FIG. 16, in an end portion, more specifically, in a corner portion 108 of each of the polishing pads 101, exfoliation is easily caused. Such exfoliation occurs for the following reason.

[0013] The polishing mechanism portion including polishing pads 101, the surface plate 102 and the carrier 103 is in a standby state in a wet atmosphere when the polishing apparatus runs at idle. Moreover, the surface plate 102 on which the polishing pads 101 are stuck continuously rotates in a conveyor belt manner with a very strong tension applied to the surface plate 102. In addition, the polishing pads 101 in polishing are exposed to a slurry and receive a pressing force against the semiconductor wafer and a contact/pressing force from the dresser. If the polishing pads 101 are in such a state for a long time, water and the slurry flow in the end portion of each of the polishing pads 101 which has a small contact area with the surface plate than those of other portions, so that exfoliation of the polishing pads occurs because of interaction with a tensile stress.

[0014] The exfoliation and the scratch 107 generated in the polishing pads 101 cause an unusual state in semiconductor processing.

[0015] First, assume that the scratch 107 exists in each of the end portion of each of the polishing pads 101 and the peripheral portion of the through hole for detecting an end point. Polishing is performed with a surface side (a principal surface side) of the semiconductor wafer 104 pressed against the polishing pads 101, so that a scratch is generated in the principal side of the wafer. The scratch generated on the principal surface side of the wafer results in drastic deterioration in reliability of a semiconductor device. This finally might cause a defect of a finished product. Therefore, a semiconductor wafer has to be examined after the semiconductor wafer has undergone through CMP and a large extra labor is required.

[0016] Next, there might be cases in which when the polishing pads 101 are exfoliated, the semiconductor wafer 104 is caught by exfoliated part of each of the polishing pads 101 in the middle of polishing and the semiconductor wafer 104 comes off from the carrier 103, thus damaging the semiconductor wafer 104.

[0017] Moreover, assume that part of the end portion of each of the polishing pads 101 is lifted up due to the exfoliation. When the lift-up part collides with the dresser 106, the dresser 106 and the cylinder 105 including the dresser 106 are damaged, so that the polishing apparatus is stopped. To make up damages, great amounts of time and expense are required.

[0018] To cope with such exfoliation of the corner portion of each of the polishing pads, measures have been taken, such as increasing an adhesion intensity of an adhesive agent for adhering the surface plate 102 and the polishing pads 101. With increased adhesion intensity between the surface plate 102 and the polishing pads 101, the surface plate 102 and the polishing pads 101 are adhered with each other with sufficient intensity immediately after sticking the polishing pads 101 to the surface plate 102. However, being rotated with a tension applied thereto and exposed to wet and chemical atmospheres, the adhesive agent is rapidly deteriorated. Moreover, depending on a slurry used, an adhesive agent has to be individually examined. Therefore, the measure of increasing an adhesion intensity of an adhesive agent is not suitable for diversified small-quantity production.

[0019] It is therefore an object of the present invention to provide polishing method and apparatus which allows polishing of a semiconductor wafer without causing the generation of a scratch and damage.

[0020] A first polishing pad according to the present invention is a polishing pad which is set under a wafer unit in chemical mechanical polishing and includes an upper surface serving as a polishing surface, wherein at least part of an upper end portion of the polishing pad has a tapered shape or a curved section.

[0021] Thus, when the first polishing pad of the present invention is used in a polishing apparatus, collision of a dresser and the upper end portion of the polishing pad can be prevented, so that the generation of the generation of a scratch around the end portion can be prevented. Therefore, polishing can be performed without causing a scratch on a wafer.

[0022] If the polishing pad has an approximately quadrangular shape when being viewed from the top and at least an upper end of part of the approximately quadrangular shape corresponding to a side is tapered or curved, the generation of a scratch around the end portion can be prevented in the case where first polishing pad is used in a belt-type polishing apparatus. Therefore, polishing can be performed without causing a scratch on a wafer, thus allowing fabrication of a highly reliable wafer.

[0023] If the polishing pad has a fan shape when being viewed from the top and said at least part of the upper end portion of the polishing pad has a tapered shape or a curved section, polishing can be performed without generating a scratch on a wafer in the case where first polishing pad is used in a turntable-type polishing apparatus in which a polishing pad is divided into a plurality of sheets.

[0024] For example, said at least part of an upper end portion is tapered and an angle of the upper end portion is an obtuse angle, collision with the dresser can be effectively prevented, so that friction with the dresser can be reduced. Therefore, the generation of a scratch around the end portion can be prevented.

[0025] If a through hole of which a peripheral portion has an upper end having a tapered shape or a curved section is further provided, the generation of a scratch around the through hole caused by the dresser can be prevented, so that polishing can be performed without causing the generation of a scratch on a wafer in the case where the first polishing pad is used in a polishing apparatus. Therefore, a more highly reliable wafer can be fabricated.

[0026] A second polishing pad according to the present invention is a polishing pad which is set under a wafer unit in chemical mechanical polishing and includes an upper surface serving as a polishing surface, wherein a first convex-and-concave portion is formed in at least part of an end portion of the polishing pad and a second convex-and-concave portion which can be exactly fitted to the first convex-and-concave portion is formed in at least part of another end portion of the polishing pad.

[0027] Thus, if the second polishing pad is adopted as a polishing pad used in a polishing apparatus and a plurality of polishing pads are connected with one another such that the first convex-and-concave portion of one of the polishing pads is exactly fitted to the second convex-and-concave portion of another one of the polishing pads, a stress from the surface plate or the wafer can be effectively dispersed. Thus, exfoliation of the polishing pads during polishing can be prevented. As a result, the polishing apparatus hardly has an emergency shutdown or other inconveniences, thus allowing reduction in costs for fabricating a semiconductor device.

[0028] If the polishing pad has, when being viewed from the top, an approximately quadrangular shape, the first convex-and-concave portion is formed on a first side and the second convex-and-concave portion is formed on an opposite side to the first side, the second polishing pad can be preferably used in a belt-type polishing apparatus.

[0029] If a through hole of which a peripheral portion has an upper end having a tapered shape or a curved section is further provided, the generation of a scratch around the through hole during polishing can be suppressed.

[0030] If a corner portion of the polishing pad, when being viewed from the top, has a tapered shape or a curved section, it is possible to make it difficult for a slurry and water to flow into the corner portions, compared to the known polishing pad. Therefore, exfoliation of the polishing pads during polishing hardly occurs when the second polishing pad of the present invention is used in a polishing apparatus.

[0031] More specifically, when being viewed from the top, the polishing pad preferably has a shape obtained by cutting off four corners or an approximately quadrangular shape with curved corners obtained by rounding four corners.

[0032] A third polishing pad according to the present invention is a polishing pad which is set under a wafer unit in chemical mechanical polishing and includes an upper surface serving as a polishing surface, where in at least part of an end portion of the polishing pad, a first protruding portion formed by making an upper part of the end portion protrude is provided and in at least part of another end portion of the polishing pad, a second protruding portion which is formed by making a lower part of the end portion and can be overlapped with the first protruding portion is provided.

[0033] Thus, assume that the third polishing pad of the present invention is adopted as a polishing pad used in a polishing apparatus and the third polishing pad is provided plural in number. If the first protruding portion is arranged in the upstream side with respect to the scanning direction of the surface plate and part of the first protruding portion and part of the second protruding portion are overlapped with each other, the generation of a scratch caused by the dresser can be suppressed. Moreover, it is possible to prevent a slurry and water from flowing into the polishing pads. Therefore, exfoliation of the polishing pads during polishing can be prevented.

[0034] If the polishing pad has an approximately quadrangular shape when being viewed from the top, the first protruding portion is formed on a first side and the second protruding portion is formed on an opposite side to the first side, the third polishing pad can be preferably used in a belt-type polishing apparatus.

[0035] A fourth polishing pad according to the present invention is a polishing pad which is set under a wafer unit in chemical mechanical polishing and includes an upper surface serving as a polishing surface, wherein a through hole of which a peripheral portion has an upper end having a tapered shape or a curved section is further provided Thus, if the fourth polishing pad of the present invention is used in a polishing apparatus, it is possible to monitor an end point of polishing through the through hole and it is also possible to prevent the generation of a scratch around the through hole.

[0036] A first polishing apparatus is a polishing apparatus which includes a surface plate, a plurality of polishing pads stuck on the surface plate so as to be spaced apart from one another and each having an upper surface serving as a polishing surface, a carrier for holding a wafer in polishing and a dresser for activating an upper surface of each of the plurality of polishing pads, and is for use in chemical mechanical polishing of the wafer, wherein an upper end portion of each said polishing pad has part facing an adjacent one of the polishing pads and having a tapered shape or a curved section.

[0037] Thus, collision of the dresser and an upper end portion of the polishing pad can be prevented, so that the generation of a scratch around the end portion can be prevented. Therefore, polishing can be performed without causing the generation of a scratch on a wafer.

[0038] The first polishing apparatus may further include at least two rollers each having a rotation shaft arranged in parallel to that of the other roller. In the first polishing apparatus, the surface plate may be a belt-type and stretched between the two rollers, and each said polishing pad may have an approximately quadrangular shape in which at least an upper end portion located on a side of the quadrangular shape is tapered or curved.

[0039] A second polishing apparatus according to the present invention is a polishing apparatus which includes a surface plate, a plurality of polishing pads stuck on the surface plate and each having an upper surface serving as a polishing surface, a carrier for holding a wafer in polishing and a dresser for activating an upper surface of each of the plurality of polishing pads, and is for use in chemical mechanical polishing of the wafer, wherein a first convex-and-concave portion is formed in at least part of an end portion of each said polishing pad and a second convex-and-concave portion which is exactly fitted to the first convex-and-concave portion of an adjacent one of the plurality of polishing pads is formed in at least part of another end portion of each said polishing pad.

[0040] Thus, if the plurality of polishing pads are connected with one another such that the first convex-and-concave portion of one of the polishing pads is exactly fitted to the second convex-and-concave portion of another one of the polishing pads, a stress applied to end portions of the polishing pads from the surface plate or the wafer can be effectively dispersed. Thus, exfoliation of the polishing pads during polishing can be prevented. As a result, the polishing apparatus hardly has an emergency shutdown or other inconveniences, thus suppressing increase in fabrication costs due to failure.

[0041] Each said polishing pad may have an approximately quadrangular shape in which the first convex-and-concave portion is formed on a first side and the second convex-and-concave portion is formed on an opposite side to the first side, when being viewed from the top.

[0042] A third polishing apparatus according to the present invention is a polishing apparatus which includes a surface plate, a plurality of polishing pads stuck on the surface plate so as to be spaced apart from one another and each having an upper surface serving as a polishing surface, a carrier for holding a wafer in polishing and a dresser for activating an upper surface of each of the plurality of polishing pads, and is for use in chemical mechanical polishing of the wafer, wherein each said polishing pad has a corner portion having a tapered shape or a curved section when being viewed from the top.

[0043] Thus, a stress applied to end portions of the polishing pads from the surface plate or the wafer can be effectively dispersed, so that exfoliation of the polishing pads during polishing hardly occurs. As a result, the polishing apparatus hardly has an emergency shutdown or other inconveniences, thus allowing reduction in costs for fabricating a semiconductor device.

[0044] A fourth polishing apparatus according to the present invention is a polishing apparatus which includes a surface plate, a plurality of polishing pads stuck on the surface plate and each having an upper surface serving as a polishing surface, a carrier for holding a wafer in polishing and a dresser for activating an upper surface of each of the plurality of polishing pads, and is for use in chemical mechanical polishing of the wafer, wherein in each said polishing pad, a first protruding portion is formed in an end portion located in the upstream side with respect to an operation direction in polishing, and wherein in each said polishing pad, a second protruding portion obtained by making lower part of the end portion protrude and be overlapped to the first protruding portion of an adjacent one of the polishing pads is formed in an end portion located in the downstream side with respect to the operation direction in polishing.

[0045] Thus, the generation of a scratch in end portions of the polishing pads caused by the dresser can be suppressed. Moreover, it is possible to prevent a slurry and water from flowing into the polishing pads. Therefore, exfoliation of the polishing pads during polishing can be prevented.

[0046] Each said polishing pad may have an approximately quadrangular shape when being viewed from the top, the first protruding portion is formed on a first side and the second protruding portion is formed on an opposite side to the first side.

[0047] A fifth polishing apparatus according to the present invention is a polishing apparatus which includes a surface plate, a plurality of polishing pads stuck on the surface plate so as to be spaced apart from one another and each having an upper surface serving as a polishing surface, a carrier for holding a wafer in polishing and a dresser for activating an upper surface of each of the plurality of polishing pads, and is for use in chemical mechanical polishing of the wafer, wherein a space between adjacent ones of the plurality of polishing pads is filled with an adhesive agent.

[0048] Thus, it is possible to prevent a slurry and water from flowing into the polishing pads. Therefore, exfoliation of the polishing pads during polishing can be prevented. Accordingly, a wafer can be smoothly polished without causing any inconveniences.

[0049] A sixth polishing apparatus is a polishing apparatus which includes a surface plate, a plurality of polishing pads stuck on the surface plate so as to be spaced apart from one another and each having an upper surface serving as a polishing surface, a carrier for holding a wafer in polishing and a dresser for activating an upper surface of each of the plurality of polishing pads, and is for use in chemical mechanical polishing of the wafer, wherein in each said polishing pad, a through hole of which a peripheral portion has an upper end having a tapered shape or a curved section is further provided.

[0050] Thus, a scratch is hardly generated in the peripheral portion of the through hole in polishing. Therefore, a polishing can be performed without causing the generation of a scratch on a wafer.

[0051] A first method for polishing a wafer is a method for polishing a wafer using a polishing apparatus which includes a surface plate and a plurality of polishing pads stuck on the surface plate and each having an upper surface serving as a polishing surface, the method comprising the steps of: a) activating the upper surface of each said polishing pad by a dresser; and b) polishing the wafer by pressing the wafer against the upper surface of each said polishing pad while scanning the surface plate, wherein each of the plurality of polishing pads used in the steps a) and b) has part of an upper end portion facing to adjacent one of the polishing pads and having a tapered shape or a curved section.

[0052] According to the first method, in the step a), a scratch is hardly generated on the polishing pads. Therefore, a wafer can be polished without generating a scratch on the wafer in the step b).

[0053] A second method for polishing a wafer according to the present invention is a method for polishing a wafer using a polishing apparatus which includes a surface plate and a plurality of polishing pads stuck on the surface plate and each having an upper surface serving as a polishing surface, the method comprising the steps of: a) activating the upper surface of each said polishing pad by a dresser; and b) polishing the wafer by pressing the wafer against the upper surface of each said polishing pad while scanning the surface plate, wherein a first convex-and-concave portion is formed in an end portion of each said polishing pad used in the steps a) and b) and a second convex-and-concave portion which is exactly fitted to the first convex-and-concave portion of an adjacent one of the polishing pads is formed in another end portion of each said polishing pad.

[0054] According to the second method, exfoliation of the polishing pads during polishing can be prevented. Therefore, emergency shutdown of a polishing apparatus and the inconveniences such as collision of the dresser and exfoliated part of each of the polishing pads in the step a) can be suppressed.

[0055] A third method for polishing a wafer according to the present invention is a method for polishing a wafer using a polishing apparatus which includes a surface plate and a plurality of polishing pads stuck on the surface plate and each having an upper surface serving as a polishing surface, the method comprising the steps of: a) activating the upper surface of each said polishing pad by a dresser; and b) polishing the wafer by pressing the wafer against the upper surface of each said polishing pad while scanning the surface plate, wherein each of the plurality of polishing pads used in the steps a) and b) has a corner portion a having a tapered shape or a curved section when being viewed from the top.

[0056] According to the third method, a stress applied to end portions of the polishing pads from the surface plate or the wafer can be effectively dispersed. Thus, exfoliation of the polishing pads during polishing can be prevented.

[0057] A fourth method for polishing a wafer according to the present invention is a method for polishing a wafer using a polishing apparatus which includes a surface plate and a plurality of polishing pads stuck on the surface plate and each having an upper surface serving as a polishing surface, the method comprising the steps of: a) activating the upper surface of each said polishing pad by a dresser; and b) polishing the wafer by pressing the wafer against the upper surface of each said polishing pad while scanning the surface plate, wherein in an end portion of each said polishing pad used in the steps a) and b) located in the upstream side with respect to the scanning direction of the surface plate, a first protruding portion obtained by making an upper portion of the end portion protrude is formed, and in another end portion of each said polishing pad located in the downstream side with respect to the scanning direction of the surface plate, a second protruding portion obtained by making a lower portion of said another end is formed.

[0058] According to the fourth method, in the step a), the generation of a scratch in end portions of the polishing pads caused by the dresser can be suppressed. Moreover, it is possible to prevent a slurry and water from flowing into the polishing pads. Therefore, exfoliation of the polishing pads during polishing can be prevented.

[0059] A fifth method for polishing a wafer is a method for polishing a wafer using a polishing apparatus which includes a surface plate and a plurality of polishing pads stuck on the surface plate and each having an upper surface serving as a polishing surface, the method comprising the steps of: a) activating the upper surface of each said polishing pad by a dresser; and b) polishing the wafer by pressing the wafer against the upper surface of each said polishing pad while scanning the surface plate, wherein a space between adjacent ones of the plurality of polishing pads used in the steps a) and b) is filled with an adhesive agent.

[0060] According to the fifth method, it is possible to prevent a slurry and water from flowing into the polishing pads. Therefore, exfoliation of the polishing pads during polishing can be prevented. Accordingly, a wafer can be smoothly polished without causing any inconveniences.

[0061] A sixth method for polishing a wafer according to the present invention is a method for polishing a wafer using a polishing apparatus which includes a surface plate and a plurality of polishing pads stuck on the surface plate and each having an upper surface serving as a polishing surface, the method comprising the steps of: a) activating the upper surface of each said polishing pad by a dresser; and b) polishing the wafer by pressing the wafer against the upper surface of each said polishing pad while scanning the surface plate, wherein in each of the plurality of polishing pads used in the steps a) and b), a through hole of which a peripheral portion has an upper end having a tapered shape or a curved section is further provided.

[0062] According to the sixth method, a scratch is hardly generated in the peripheral portion of the through hole in polishing. Therefore, a polishing can be performed without causing the generation of a scratch on a wafer.

BRIEF DESCRIPTION OF THE DRAWINGS

[0063]FIG. 1 is a schematic view illustrating the structure of a polishing mechanism portion of a belt-polishing type CMP apparatus according to a first embodiment of the present invention.

[0064]FIG. 2 is an enlarged perspective view illustrating a portion A in the CMP apparatus of the first embodiment shown in FIG. 1.

[0065]FIG. 3 is an enlarged cross-sectional view in the length direction illustrating the portion A in the CMP apparatus of the first embodiment.

[0066]FIG. 4 is an enlarged cross-sectional view illustrating a modified example of the portion A of FIG. 1 in the CMP apparatus of the first embodiment.

[0067]FIG. 5 is an enlarged cross-sectional view illustrating another modified example of the portion A of FIG. 1 in the CMP apparatus of the first embodiment.

[0068]FIG. 6 is an enlarged perspective view of a portion B of a polishing pad of the CMP apparatus of the first embodiment.

[0069]FIG. 7 is an enlarged cross-sectional view illustrating the portion B of the polishing pad of the CMP apparatus of FIG. 1.

[0070]FIG. 8 is a perspective view illustrating a polishing pad used in a CMP apparatus according to a second embodiment of the present invention.

[0071]FIG. 9 is a perspective view illustrating a polishing pad used in a CMP apparatus according to a third embodiment of the present invention.

[0072]FIG. 10 is a perspective view illustrating a polishing pad used in a CMP apparatus according to a fourth embodiment of the present invention.

[0073]FIG. 11 is an enlarged cross-sectional view illustrating a portion C of FIG. 10 in the polishing pad of the fourth embodiment.

[0074]FIG. 12 is a perspective view illustrating a structure between polishing pads in a CMP apparatus according to a fifth embodiment of the present invention.

[0075]FIG. 13 is a cross-sectional view in the length direction, illustrating an end portion of a polishing pad and a surface plate of the CMP apparatus of the fifth embodiment.

[0076]FIG. 14A is a side view of a CMP apparatus according to a sixth embodiment of the present invention.

[0077]FIG. 14B is a plan view of the CMP apparatus of the sixth embodiment when a polishing pad is viewed from the top.

[0078]FIG. 15 is a schematic view illustrating the structure of a polishing mechanism portion of a known belt polishing type CMP apparatus.

[0079]FIG. 16 is an enlarged view of a portion E in the known CMP apparatus of FIG. 15 illustrating the through hole 110 for polishing end pond detection.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0080] In order to prevent polishing pads from being damaged in a belt-type polishing apparatus, the present inventors first made an attempt to rationalize an interval between adjacent two of a plurality of sheet-type polishing pads and improve a dresser. However, with a currently used polishing mechanism, a scratch made on polishing pads could not be markedly reduced. Moreover, although different base materials were examined for use in polishing pads, it was difficult to select a base material which allows proper polishing of a wafer and does not generate a scratch in polishing pads. Then, the present inventors took a notice of an end portion of a polishing pad, including a corner portion, and changed the shape of the end portion of the sheet-type polishing pad. As a result, it was confirmed that change of the shape of an end portion can prevent collision of a dresser and polishing pads, so that the generation of a scratch in the polishing pads can be suppressed.

[0081] Specifically, in the polishing apparatus, part of an upper portion of each of the polishing pads facing an adjacent polishing pad has a tapered (chamfered) shape or a curved section, so that the upper portion of each of the polishing pads and a dresser were not collided with each other. Accordingly, the generation of a scratch can be suppressed. Moreover, when the same processing was performed to through holes of polishing pads, the rate of the generation of a scratch in a peripheral portion of each of the through holes was markedly reduced, compared to the known polishing apparatus. Note that in this specification, “rounding (curving)” is a method for rounding a corner portion or a corner of an upper portion.

[0082] Meanwhile, it was also confirmed that the end portion of the corner portion of each of the polishing pads was processed to have a shape with which a tension from a surface plate and a stress from the dresser and the wafer were hardly concentrated, thereby suppressing separation of the polishing pads from the surface plate. Moreover, by making the shape of the end portion into a shape with which a slurry and water hardly flow into between the surface plate and the polishing pads, exfoliation of the polishing pads could be suppressed.

[0083] Hereinafter, embodiments of the present invention which the present inventors have reached in the above-described manner will be described with reference to the accompanying drawings.

[0084] (First Embodiment)

[0085]FIG. 1 is a schematic view illustrating the structure of a polishing mechanism portion of a belt-polishing type CMP apparatus according to a first embodiment of the present invention.

[0086] As shown in FIG. 1, the polishing mechanism portion of the CMP apparatus of this embodiment includes two rollers (pulleys) 1 each having a rotation shaft arranged in parallel to that of the other roller, a surface plate 2 stretched between the two rollers 1, a plurality of sheet-type polishing pads 3 (e.g., four polishing pads 3 in this embodiment) stuck on an outer surface of the surface plate 2 with an adhesive sheet or the like, a carrier 16 for holding a semiconductor wafer 5 in polishing, a cylinder 6, a dresser 7 for activating (raising a nap on) an upper surface of each of the polishing pads, and a detector (not shown) for detecting an end portion of polishing. Each of the polishing pads 3 is made of, for example, polyurethane, more specifically, closed-cell-foam polyurethane and has a rectangular shape.

[0087] Moreover, a through hole 8 for detecting an end point of polishing is formed in each of the surface plate 2 and the polishing pads 3. The through hole 8 is a through hole through which light such as a laser beam irradiated from the detector provided under the surface plate 2 passes. The detector detects a laser beam reflected on a semiconductor wafer, thereby detecting an end portion of polishing.

[0088] A method for polishing a semiconductor wafer using the CMP apparatus (polishing apparatus) of this embodiment is the same as a known method for polishing a semiconductor wafer.

[0089] Specifically, in polishing, the semiconductor wafer 5 is held by the carrier 16 so that the principal surface side of the semiconductor wafer 5 is directly in contact with each of the polishing pads. The carrier 16 is rotated with a line which is perpendicular to a wafer surface to be polished and includes the center of the semiconductor wafer 5 as an axis.

[0090] The belt-type surface plate 2 is rotated in a so-called “conveyor belt manner”.

[0091] In polishing, the dresser 7 provided on a lower surface of the cylinder 6 is in contact with an upper surface of one of the polishing pads 3 and performs dressing to the polishing pads 3 while moving in the perpendicular direction to a forward direction in which the polishing pads 3 moves, thereby raising a nap on an upper surface of each of polishing pads 3. Note that in a polishing surface of each of the polishing pads 3, a perpendicular direction to the forward direction is referred to as a “width direction” and a parallel direction to the forward direction is referred to as a “length direction”.

[0092] In this manner, the semiconductor wafer 5 is rotated while the polishing pads 3 moves in the forward direction, thereby performing polishing. In this case, a slurry containing polishing particles is supplied to the polishing pads 3.

[0093] Next, the shape of end portion of the polishing pads and the shape of peripheral portion of the through hole 8 which characterize the polishing pads 3 of this embodiment will be described.

[0094]FIG. 2 is an enlarged perspective view illustrating a portion A in the CMP apparatus of this embodiment shown in FIG. 1. FIG. 3 is an enlarged cross-sectional view in the length direction illustrating the portion A in the CMP apparatus of this embodiment. Note that the portion A of FIG. 1 is a joint portion in which one of the plurality of polishing pads 3 are jointed to the surface plate 2.

[0095] As shown in FIGS. 2 and 3, in the CMP apparatus of this embodiment, part of an upper portion of each of the polishing pads 3 facing an adjacent one of the polishing pads 3 (an end portion 4) is obliquely cut. Thus, as shown in FIG. 3, part of the surface plate 2 and a side end surface of each of the polishing pads 3 make an acute angle and an upper end portion of each of the polishing pads 3 is an obtuse angle.

[0096] Thus, in polishing, the polishing pads 3 are activated without having the dresser 7 caught by the upper portion of each of the polishing pads 3, so that the generation of a scratch, which occurs in the known apparatus, can be prevented. Therefore, with the CMP apparatus of this embodiment, CMP can be performed without causing the generation of a scratch on the principal surface of a semiconductor wafer.

[0097] Specifically, in the CMP apparatus of this embodiment, a lower end portion of each of the polishing pads 3 is an acute angle. Thus, the dresser 7 is less likely to be caught by the polishing pads 3. Note that this shape can be formed in a simple manner by general tapering.

[0098] Moreover, FIGS. 1 through 3 show an example in which the polishing pads 3 are stuck on the surface plate 2 so as to be spaced apart from one another. However, the polishing pads 3 may be arranged without a space therebetween. Even when the polishing pads 3 of this embodiment are arrange without a space therebetween, a space for exhausting a slurry and polishing wastes can be ensured. Therefore, an excellent polishing can be continued while keeping a slurry and water from flowing into the back surface of each of the polishing pads 3.

[0099] Moreover, FIGS. 4 and 5 are enlarged cross-sectional views illustrating a modified example of the portion A of FIG. 1.

[0100] Even when the end portion 4 of each of the polishing pads 3 has a shape obtained by chamfering (tapering) of an upper end portion thereof, the above-described effects can be achieved. Specifically, part of the upper end portion of each of the polishing pads 3 facing adjacent one of the polishing pad may be an angle of 90 degrees or more, i.e., an obtuse angle. In that case, the upper end portion of each of the polishing pads 3 hardly collides with the dresser 7. Accordingly, a scratch is hardly generated in the end portion 4 of each of the polishing pads 3.

[0101] Moreover, the end portion 4 of each of the polishing pads 3 may be rounded, as shown in FIG. 5. In the manner shown in FIG. 5, even when the upper end portion of each of the polishing pads 3 is rounded by a cutter, a file or the like, the upper end portion of each of the polishing pads 3 is hardly caught by the dresser 7.

[0102] Moreover, when the same processing as the above-described processing performed to the end portions of the polishing pads 3 is performed to the peripheral portion of the through hole 8, the same effects can be achieved.

[0103]FIG. 6 is an enlarged perspective view of a portion B of a polishing pad of the CMP apparatus of FIG. 1. FIG. 7 is an enlarged cross-sectional view illustrating the portion B of the polishing pad of the CMP apparatus of FIG. 1. Note that in FIG. 1, the portion B is the through hole 8. Moreover, FIG. 7 illustrates a cross section of the surface plate 2 and the polishing pads 3 in the length direction.

[0104] As shown in FIGS. 6 and 7, the polishing pads 3 used in the CMP apparatus of this embodiment, the angle of an upper end of a peripheral portion 9 of the through hole 8 is an obtuse angle in a cross section in the length direction.

[0105] Thus, in the peripheral portion 9 of the through hole 8, the upper end portion of each of the polishing pads 3 hardly collides with the dresser 7, so that the generation of a scratch which occurs in an upper surface of a semiconductor wafer in the known apparatus can be suppressed. Moreover, the polishing pads 3 can be safely and smoothly activated by the dresser 7.

[0106] Note that as the end portion 4 of FIG. 3, a shape obtained by obliquely cutting the peripheral portion 9 of the through hole 8 may be adopted, and as the end portion of FIG. 5, an upper end of the peripheral portion of the through hole 8 may be rounded. In those cases, collision of the dresser 7 and the peripheral portion 9 can be suppressed. Therefore, a scratch is hardly generated in the peripheral portion 9.

[0107] As has been described, in the CMP apparatus of this embodiment, the shape of the end portion 4 of each of the polishing pads 3 and the shape of the peripheral portion of the through hole 8 are changed so that the dresser 7 is hardly caught or friction is reduced. Thus, the generation of a scratch in the polishing pads 3 is suppressed.

[0108] Note that examples in which in the polishing pads 3 used in the CMP apparatus of this embodiment, both of end portions of each of the polishing pads 3 in the length direction, i.e., end portions located in the upstream side and the downstream side with respect to the forward direction are processed have been described in FIGS. 2 through 5. However, even when only an end portion located in the downstream side is processed, the same effects as those of the example can be achieved. The case in which both of end portions of each of the polishing pads 3 located in the upstream side and the down stream side are processed is more preferable because positioning adjustment in sticking the polishing pads 3 can be performed in a more simple manner and the polishing pads 3 can be installed in the apparatus with no concern about the direction of the polishing pads 3.

[0109] Moreover, in this embodiment, an example in which the four polishing pads 3 are stuck on the belt-type surface plate 2 in each CMP apparatus has been described. However, the number of the polishing pads 3 is not particularly limited. The width of the polishing pads 3 is preferably at least larger than the diameter of the semiconductor wafer and has a proper margin.

[0110] (Second Embodiment)

[0111]FIG. 8 is a perspective view illustrating a polishing pad used in a CMP apparatus according to a second embodiment of the present invention. Note that in FIG. 8, each member also described in the first embodiment is identified by the same reference numeral. Moreover, the CMP apparatus of this embodiment is the same as that of the first embodiment except for the shape of polishing pads and the manner in which the polishing pads are stuck. Therefore, only the shape of polishing pads and the manner in which the polishing pads are stuck will be hereinafter described.

[0112] As shown in FIG. 8, in each of polishing pads 3 of this embodiment, a convex-and-concave portion 10 is formed in the upstream or downstream side with respect to the forward direction. The shape of the convex-and-concave portion 10 is made so that the convex-and-concave portion 10 can be exactly fitted to that of an adjacent one of the polishing pads 3.

[0113] In the CMP apparatus of this embodiment, with the convex-and-concave portion 10 of each of the polishing pads 3 exactly fitted to that of an adjacent one of the polishing pads 3, the plurality of polishing pads 3 are stuck on a surface place 2 without any space therebetween.

[0114] The shape of each of the convex-and-concave portions 10 is not particularly limited, as long as the convex-and-concave portion 10 of each of the polishing pads 3 can be exactly fitted to that of an adjacent one of the polishing pads 3. Moreover, the numbers of convex and concave parts to be formed is not limited.

[0115] With the convex-and-concave portions 10 provided in each of the polishing pads 3, a contact area of adjacent ones of the polishing pads 3 is increased. Accordingly, a tension (tensile strength) applied to the polishing pads 3 can be dispersed. Furthermore, an adhesion surface of the surface plate 2 and each of polishing pads 3 can be kept from being directly in contact with wet/chemical atmosphere. Accordingly, exfoliation of end portions, more specifically, corner portions of the polishing pads 3 can be suppressed. Therefore, in the CMP apparatus using the polishing pad of this embodiment, emergency shutdown due to exfoliation of the polishing pads or other inconveniences hardly occur. Moreover, the lifetime of each of polishing pads 3 can be increased, thus resulting in reduction in fabrication costs.

[0116] (Third Embodiment)

[0117]FIG. 9 is a perspective view illustrating a polishing pad used in a CMP apparatus according to a third embodiment of the present invention.

[0118] As shown in FIG. 9, each of polishing pads 3 used in the CMP apparatus of this embodiment includes a corner portion 11 with a corner shaved off by chamfering or the like when being viewed from the top. By such processing, the angle of each corner portion can be made to be 90 degrees or more when being viewed from the top. Note that in addition to conferring of the corner portion, a side end surface of the corner portion 11 may be rounded so as to have a curved surface such as a circular shape.

[0119] The known polishing pad has a rectangular shape, so that a tension applied from the surface plate 2 is concentrated in a corner portion and moreover a slurry and water easily flow therein. However, in the CMP apparatus of this embodiment, each of the polishing pads 3 has a shape with a corner of the corner portion 11 shaved off. Thus, a stress which the polishing pads 3 receive can be dispersed according to a tension (tensile strength) applied to the surface plate 2, so that exfoliation of the polishing pads 3 hardly occurs. Moreover, a liquid such as a slurry and water can hardly flow into the adhesion portion of the surface plate 2 and each of the polishing pads 3. This also prevents exfoliation of the polishing pads 3. Therefore, with the CMP apparatus of this embodiment, the generation of troubles such as emergency shutdown in polishing can be suppressed.

[0120] Note that to ensure an area in which a semiconductor wafer is polished, in each of the polishing pads 3 of this embodiment, the range in which the above-described conferring or rounding process is performed is preferably located in a region extending by about 40 mm or less from an width-direction end portion of each of the polishing pads 3.

[0121] (Fourth Embodiment)

[0122]FIG. 10 is a perspective view illustrating a polishing pad used in a CMP apparatus according to a fourth embodiment of the present invention. Moreover, FIG. 11 is an enlarged cross-sectional view illustrating a portion C of FIG. 10 in the polishing pad of this embodiment. Note that FIG. 11 illustrates a cross section of the surface plate 2 and the polishing pads 3 in the forward direction (the length direction) of the surface plate 2.

[0123] As shown in FIG. 11, a notch potion 12 is formed in each of end portions of each of the polishing pads 3 of this embodiment located in the upstream side and the downstream side with respect to the forward direction. In the notch portion 12 located in the upstream-side end portion with respect to the forward direction, an upper part is protruding, compared to a lower part. In the notch portion 12 located in the downstream-side end portion, a lower part is protruding so that the upstream-side end portion is exactly fitted to the downstream-side end portion. The shapes of protruding parts of the upstream- and downstream-side end portions are not particularly limited, as long as the upstream-side and downstream-side end portions are exactly fitted to each other. Whether the step-like shape shown in FIG. 11 should be formed, or the upstream- and downstream-side end portions should be obliquely cut is determined in fabrication stage, for example, after it has been examined which is more suitable for a material of polishing pads.

[0124] In the CMP apparatus of this embodiment, the above-described plurality of polishing pads 3 are stuck on the surface plate 2 with the notch portions 12 in end portions of the polishing pads 3 overlapped to each other. In this case, as shown in FIG. 11, the downstream-side notch portion 12 of one the polishing pads 3 located in the upstream side overlaps the upstream-side notch portion 12 of another one of the polishing pads 3 located in the downstream side. Thus, in polishing the semiconductor wafer 5 (see FIG. 1), the dresser 7 is hardly caught by end portions of the polishing pads 3, so that the polishing pads can be smoothly activated. Accordingly, polishing can be performed without causing the generation of a scratch on the principal surface of the semiconductor wafer 5. Moreover, by forming the notch portion 12 in an end portion of each of the polishing pads 3, a contact interface of the surface plate 2 and each of the polishing pads 3 can be kept from being in contact with a wet atmosphere and a chemical atmosphere, so that exfoliation of the polishing pads 3 can be suppressed. Therefore, processing of a semiconductor wafer can be smoothly performed.

[0125] (Fifth Embodiment)

[0126]FIG. 12 is a perspective view illustrating a structure between polishing pads in a CMP apparatus according to a fifth embodiment of the present invention. FIG. 13 is a cross-sectional view in the length direction, illustrating an end portion of a polishing pad and a surface plate of the CMP apparatus of this embodiment.

[0127] As shown in FIG. 12, in the CMP apparatus of this embodiment, a plurality of polishing pads 3 are stuck on a surface plate 2 and an adhesive agent 13 is applied in a space between adjacent ones of the polishing pads 3. The adhesive agent 13 is applied, for example, when the polishing pads 3 are being stuck on the surface plate 2, and then is hardened.

[0128] Moreover, the adhesive agent 13 is applied so as not to be higher than the polishing pads 3 and have a portion protruding out from the space after being hardened.

[0129] Thus, a semiconductor wafer can be polished with an adhesion interface of the surface plate and each of the polishing pads 3 not being in direct contact with a wet atmosphere and a chemical atmosphere. Accordingly, exfoliation of an end portion of each of the polishing pads 3 can be prevented in polishing. Moreover, end portions of the polishing pads 3 are physically adhered to the surface plate with the adhesive agent 13, so that the polishing pads 3 even less likely peel off.

[0130] As the adhesive agent used in this case, for example, an epoxy thermosetting type agent which has high chemical resistance and can be hardened in a simple manner is preferably used. Specifically, an epoxy resin has excellent elasticity and thus can release a stress applied to the polishing pads 3. With such an adhesive agent, after the polishing pads 3 have been stuck on the surface plate 2, an adhesive agent is applied between the polishing pads 3 and then hardened by a heat source such as a dryer. Thereafter, a semiconductor wafer is polished.

[0131] Note that in FIG. 13, an example in which the upper end portion of each of the polishing pads 3 is rounded is shown. However, the shape of the polishing pads 3 may be the same as that in the known apparatus and may be the same as that of the first and third embodiments. However, when the polishing pad of the first embodiment is used, a scratch is hardly generated in polishing, and furthermore, exfoliation of the polishing pad hardly occurs, so that additive effects can be expected. When the polishing pad of the third embodiment is used, the effect of suppressing exfoliation of the polishing pad can be preferably increased.

[0132] (Sixth Embodiment)

[0133] In each of the above-described embodiments, examples in which the end portion of each of the polishing pads is processed in the belt-polishing type CMP apparatus have been described. There are also cases in which in a turntable-type CMP apparatus, an end portion of a polishing pad needs to be processed.

[0134] In a known turntable-type CMP apparatus, a circular polishing pad is stuck on an upper surface of a surface plate having a disc shape. Polishing is performed by pressing a semiconductor wafer or a dresser against the polishing pad from above. In the known CMP apparatus, only a sheet of circular polishing pad is used. Therefore, the known turntable-type CMP apparatus do not inconveniences such as the generation of a scratch in an end portion of a polishing pad and emergency shutdown due to exfoliation of end portions, which have been taken up as problems that the present invention solves. However, in the known turntable-type CMP apparatus, a larger polishing pad than that of a belt-polishing type CMP apparatus is used, so that it is therefore difficult to stick the polishing pad to the surface plate without containing any foam between the polishing pad and the surface plate. The existence of such foams causes inconveniences in many cases. Moreover, even when the polishing pad has only one portion containing forms or a rip, the whole polishing pad has to be replaced. This causes increase in fabrication costs.

[0135] To solve the problem, turntable-type CMP apparatus in which a polishing pad is divided into several pieces has been proposed. With a polishing pad divided into several pieces, foams hardly exists between the polishing pad and the polishing surface plate in sticking the polishing pad and the polishing surface plate. Thus, when the polishing pad is being stuck on the polishing surface plate, the polishing pad does not deflect. Furthermore, damaged part of the polishing pad can be partially exchanged, so that costs for the polishing pad can be reduced. In addition, with the polishing pad divided into several pieces, sticking and peeling of the polishing pad can be performed in a simple manner.

[0136] However, dividing a circular pad into several pieces has caused problems such as exfoliation of the polishing pad and the generation of a scratch as in a belt-polishing type CMP apparatus.

[0137] Then, the present inventors thought that a method for processing an end portion of a polishing pad, which has been effective in belt-polishing type CMP could be applied to turntable-type CMP.

[0138]FIG. 14A is a side view of a CMP apparatus according to a sixth embodiment of the present invention. FIG. 14B is a plan view of the CMP apparatus of this embodiment when a polishing pad is viewed from the top.

[0139] As shown in FIG. 14A, the CMP apparatus of this embodiment includes a surface plate 21, a polishing pad 22 stuck on an upper surface of the surface plate 21, a carrier 24 which includes a rotating mechanism and a pressuring mechanism and holds a semiconductor wafer 23, and a dresser 26 which includes a rotating mechanism and pressuring mechanism and raises a nap on the upper surface of the polishing pad 22.

[0140] As shown in FIG. 14B, the polishing pad 22 of this embodiment has a shape obtained by dividing the known polishing pad into several pieces. For example, in the CMP apparatus of this embodiment, four fan-shaped polishing pads 22 are stuck to the surface plate 21 with no space therebetween. Part of each of the polishing pads 22 being in contact with an adjacent one of the polishing pads, i.e., an end portion of each of the polishing pads 22 is tapered.

[0141] In this manner, corners of corner portions located in parts of the polishing pads stuck to each other are cut off or tapered polishing pads are stuck on a surface plate, thereby preventing the dresser from being caught by the stuck parts of the polishing pads 22. Accordingly, a scratch generated when the dresser is caught by the stuck parts can be prevented, so that a slurry and polishing wastes remaining after polishing can be effectively exhausted in the outward direction of the polishing pads 22.

[0142] Besides, convex-and-concave portions may be formed on a side of each of the polishing pads 22 and then with the convex-and-concave portions of adjacent ones of the polishing pads 22 fitted to one another, the polishing pads 22 may be stuck on the surface plate 21. Moreover, a space between adjacent ones of the polishing pads may be filled with an adhesive agent, thereby preventing moisture and a slurry from entering into an adhesion portion between the surface plate 21 and each of the polishing pads 22.

[0143] Note that in FIG. 14B, four polishing pads 22 are stuck on the surface plate 21. However, the number of the polishing pads 22 is not particularly limited. 

What is claimed is:
 1. A polishing pad which is set under a wafer unit in chemical mechanical polishing and includes an upper surface serving as a polishing surface, wherein at least part of an upper end portion of the polishing pad has a tapered shape or a curved section.
 2. The polishing pad of claim 1, wherein the polishing pad has an approximately quadrangular shape when being viewed from the top and at least an upper end of part of the approximately quadrangular shape corresponding to a side is tapered or curved.
 3. The polishing pad of claim 1, wherein the polishing pad has a fan shape when being viewed from the top and said at least part of the upper end portion of the polishing pad has a tapered shape or a curved section.
 4. The polishing pad of claim 1, wherein said at least part of an upper end portion is tapered and an angle of the upper end portion is an obtuse angle.
 5. The polishing pad of claim 1, wherein a through hole of which a peripheral portion has an upper end having a tapered shape or a curved section is further provided.
 6. A polishing pad which is set under a wafer unit in chemical mechanical polishing and includes an upper surface serving as a polishing surface, wherein a first convex-and-concave portion is formed in at least part of an end portion of the polishing pad and a second convex-and-concave portion which can be exactly fitted to the first convex-and-concave portion is formed in at least part of another end portion of the polishing pad.
 7. The polishing pad of claim 6, wherein when being viewed from the top, the polishing pad has an approximately quadrangular shape, the first convex-and-concave portion is formed on a first side and the second convex-and-concave portion is formed on an opposite side to the first side.
 8. The polishing pad of claim 6, wherein a through hole of which a peripheral portion has an upper end having a tapered shape or a curved section is further provided.
 9. A polishing pad which is set under a wafer unit in chemical mechanical polishing and includes an upper surface serving as a polishing surface, wherein a corner portion of the polishing pad, when being viewed from the top, has a tapered shape or a curved section.
 10. The polishing pad of claim 9, wherein when being viewed from the top, the polishing pad has a shape obtained by cutting off four corners or an approximately quadrangular shape with curved corners obtained by rounding four corners.
 11. The polishing pad of claim 9, wherein a through hole of which a peripheral portion has an upper end having a tapered shape or a curved section is further provided.
 12. A polishing pad which is set under a wafer unit in chemical mechanical polishing and includes an upper surface serving as a polishing surface, wherein in at least part of an end portion of the polishing pad, a first protruding portion formed by making an upper part of the end portion protrude is provided and in at least part of another end portion of the polishing pad, a second protruding portion which is formed by making a lower part of the end portion and can be overlapped with the first protruding portion is provided.
 13. The polishing pad of claim 12, wherein the polishing pad has an approximately quadrangular shape when being viewed from the top, the first protruding portion is formed on a first side and the second protruding portion is formed on an opposite side to the first side.
 14. The polishing pad of claim 12, wherein a through hole of which a peripheral portion has an upper end having a tapered shape or a curved section is further provided.
 15. A polishing pad which is set under a wafer unit in chemical mechanical polishing and includes an upper surface serving as a polishing surface, wherein a through hole of which a peripheral portion has an upper end having a tapered shape or a curved section is further provided.
 16. A polishing apparatus which includes a surface plate, a plurality of polishing pads stuck on the surface plate so as to be spaced apart from one another and each having an upper surface serving as a polishing surface, a carrier for holding a wafer in polishing and a dresser for activating an upper surface of each of the plurality of polishing pads, and is for use in chemical mechanical polishing of the wafer, wherein an upper end portion of each said polishing pad has part facing an adjacent one of the polishing pads and having a tapered shape or a curved section.
 17. The polishing apparatus of claim 16, further comprising at least two rollers each having a rotation shaft arranged in parallel to that of the other roller, wherein the surface plate is a belt-type and stretched between the two rollers, and wherein each said polishing pad has an approximately quadrangular shape in which at least an upper end portion located on a side of the quadrangular shape is tapered or curved.
 18. A polishing apparatus which includes a surface plate, a plurality of polishing pads stuck on the surface plate and each having an upper surface serving as a polishing surface, a carrier for holding a wafer in polishing and a dresser for activating an upper surface of each of the plurality of polishing pads, and is for use in chemical mechanical polishing of the wafer, wherein a first convex-and-concave portion is formed in at least part of an end portion of each said polishing pad and a second convex-and-concave portion which is exactly fitted to the first convex-and-concave portion of an adjacent one of the plurality of polishing pads is formed in at least part of another end portion each said polishing pad.
 19. The polishing apparatus of claim 18, wherein each said polishing pad has an approximately quadrangular shape in which the first convex-and-concave portion is formed on a first side and the second convex-and-concave portion is formed on an opposite side to the first side, when being viewed from the top.
 20. A polishing apparatus which includes a surface plate, a plurality of polishing pads stuck on the surface plate so as to be spaced apart from one another and each having an upper surface serving as a polishing surface, a carrier for holding a wafer in polishing and a dresser for activating an upper surface of each of the plurality of polishing pads, and is for use in chemical mechanical polishing of the wafer, wherein each said polishing pad has a corner portion having a tapered shape or a curved section when being viewed from the top.
 21. A polishing apparatus which includes a surface plate, a plurality of polishing pads stuck on the surface plate and each having an upper surface serving as a polishing surface, a carrier for holding a wafer in polishing and a dresser for activating an upper surface of each of the plurality of polishing pads, and is for use in chemical mechanical polishing of the wafer, wherein in each said polishing pad, a first protruding portion is formed in an end portion located in the upstream side with respect to an operation direction in polishing and in each said polishing pad, a second protruding portion obtained by making lower part of the end portion protrude and be overlapped to the first protruding portion of an adjacent one of the polishing pads is formed in an end portion located in the downstream side with respect to the operation direction in polishing.
 22. The polishing apparatus of claim 21, wherein each said polishing pad has an approximately quadrangular shape when being viewed from the top, the first protruding portion is formed on a first side and the second protruding portion is formed on an opposite side to the first side.
 23. A polishing apparatus which includes a surface plate, a plurality of polishing pads stuck on the surface plate so as to be spaced apart from one another and each having an upper surface serving as a polishing surface, a carrier for holding a wafer in polishing and a dresser for activating an upper surface of each of the plurality of polishing pads, and is for use in chemical mechanical polishing of the wafer, wherein a space between adjacent ones of the plurality of polishing pads is filled with an adhesive agent.
 24. A polishing apparatus which includes a surface plate, a plurality of polishing pads stuck on the surface plate so as to be spaced apart from one another and each having an upper surface serving as a polishing surface, a carrier for holding a wafer in polishing and a dresser for activating an upper surface of each of the plurality of polishing pads, and is for use in chemical mechanical polishing of the wafer, wherein in each said polishing pad, a through hole of which a peripheral portion has an upper end having a tapered shape or a curved section is further provided.
 25. A method for polishing a wafer using a polishing apparatus which includes a surface plate and a plurality of polishing pads stuck on the surface plate and each having an upper surface serving as a polishing surface, the method comprising the steps of: a) activating the upper surface of each said polishing pad by a dresser; and b) polishing the wafer by pressing the wafer against the upper surface of each said polishing pad while scanning the surface plate, wherein each of the plurality of polishing pads used in the steps a) and b) has part of an upper end portion facing to adjacent one of the polishing pads and having a tapered shape or a curved section.
 26. A method for polishing a wafer using a polishing apparatus which includes a surface plate and a plurality of polishing pads stuck on the surface plate and each having an upper surface serving as a polishing surface, the method comprising the steps of: a) activating the upper surface of each said polishing pad by a dresser; and b) polishing the wafer by pressing the wafer against the upper surface of each said polishing pad while scanning the surface plate, wherein a first convex-and-concave portion is formed in an end portion of each said polishing pad used in the steps a) and b) and a second convex-and-concave portion which is exactly fitted to the first convex-and-concave portion of an adjacent one of the polishing pads is formed in another end portion of each said polishing pad.
 27. A method for polishing a wafer using a polishing apparatus which includes a surface plate and a plurality of polishing pads stuck on the surface plate and each having an upper surface serving as a polishing surface, the method comprising the steps of: a) activating the upper surface of each said polishing pad by a dresser; and b) polishing the wafer by pressing the wafer against the upper surface of each said polishing pad while scanning the surface plate, wherein each of the plurality of polishing pads used in the steps a) and b) has a corner portion having a tapered shape or curved section when being viewed from the top.
 28. A method for polishing a wafer using a polishing apparatus which includes a surface plate and a plurality of polishing pads stuck on the surface plate and each having an upper surface serving as a polishing surface, the method comprising the steps of: a) activating the upper surface of each said polishing pad by a dresser; and b) polishing the wafer by pressing the wafer against the upper surface of each said polishing pad while scanning the surface plate, wherein in an end portion of each said polishing pad used in the steps a) and b) located in the upstream side with respect to the scanning direction of the surface plate, a first protruding portion obtained by making an upper portion of the end portion protrude is formed, and in another end portion of each said polishing pad located in the downstream side with respect to the scanning direction of the surface plate, a second protruding portion obtained by making a lower portion of said another end is formed.
 29. A method for polishing a wafer using a polishing apparatus which includes a surface plate and a plurality of polishing pads stuck on the surface plate and each having an upper surface serving as a polishing surface, the method comprising the steps of: a) activating the upper surface of each said polishing pad by a dresser; and b) polishing the wafer by pressing the wafer against the upper surface of each said polishing pad while scanning the surface plate, wherein a space between adjacent ones of the plurality of polishing pads used in the steps a) and b) is filled with an adhesive agent.
 30. A method for polishing a wafer using a polishing apparatus which includes a surface plate and a plurality of polishing pads stuck on the surface plate and each having an upper surface serving as a polishing surface, the method comprising the steps of: a) activating the upper surface of each said polishing pad by a dresser; and b) polishing the wafer by pressing the wafer against the upper surface of each said polishing pad while scanning the surface plate, wherein in each of the plurality of polishing pads used in the steps a) and b), a through hole of which a peripheral portion has an upper end having a tapered shape or a curved section is further provided. 